1. Lecture 9 Nucleus - Forces ASTR 340 Fall 2006 Dennis Papadopoulos

2. FIRST IN CLASS EXAM ON THURSDAY OCT. 5 3.30-5.00 PM. BRING CALCULATOR. YOU CAN HAVE ONE PAGE OF NOTES EXAMS COVERS ALL LECTURES – GO OVER THE POWERPOINTS IN WEB, CHAPTERS 1- 4 AND CHAPTER 6 PAGES 165-173.

3. Table 13-1, p.465

4. Mass-Energy Equivalence PREVIEW E=mc 2 EQUIVALENCE OF MASS AND ENERGY MASS+ENERGY CONSERVED MASS TRANSFORME INTO ENERGY AND ENERGY INTO MASS E=9x10 16 (m/kg) Joules From Lecture 5 we found energy of a 1kg (e.g. steak) 4.5 MJ (1000 cal) In chemical reactions we get an efficiency of transforming mass into energy approximately 4.5x10 6 /9x10 16 =5x10 -11 Chemical bond – Electromagnetic Force – e.g. NaCl In chemical reactions only the energy stored in outer electrons is released Nucleus does not play any role

5. Covalent bond

6. Fig. 13-3, p.468 Nucleus involves only protons and neutrons (nucleons) Electrostatic repulsion of protons balanced by the nuclear force. Strong but short range – nearest neighbor. The Nuclear Force

7. Fig. 13-4, p.469

8. Binding Energy: A nucleus is dismantled by removing a nucleon at a time and the amount of work done in the process is measured. Next if we next reassemble the nucleons in the form of the original nucleus, an amount of energy equal to the work done would be released. This is the called the binding energy of the nucleus. It indicates how tightly bound is. Key quantity is the binding energy per nucleon. It is the binding energy divided by the number of nucleons. Curve of the binding energy

9. Nuclear Binding Energy

10. Fusion - Fission

12. Fusion - Issues

13. Fusion Cycles

14. CNO Cycle

15. Fig. 13-12, p.478 Fission

16. Chain Reaction

17. DOUBLING TIMES Doubling time Growth factor 1 2 1 =2 2 2 2 =4 4 2 4 =16 10 2 10 =1024 25 3.3x10 7 50 1.1x10 15 80 1.2x10 24 Critical Mass Energy per U 235 fission 235 MeV

18. Fig. 14-6, p.514

19. Table 13-3, p.483

20. Energy per nucleon required to put together the nucleus of an element as a function of the mass number

21. Fig. 13-14, p.481

22. Radioactivityalpha decay Ra(226,88)->Rn(222,86)+He(4,2) U(238,92)->Th(234,90)+He(4,2) Beta decay C(14,6)->N(14,7)+e - +

23. Fig. 13-16, p.485

24. Fig. 13-15, p.482 Radioactive Dating U 238 ->Pb 206 determines when rocks were solidified 3.9 byears, meteorites 4.6 byears

25. Fig. 14-10, p.516

26. Fig. 14-14a, p.522

27. Fig. 14-14b, p.522

28. Fig. 14-15, p.523

29. Fig. 14-16, p.524

30. Fig. 14-17, p.525

31. Fig. 14-18, p.526

32. Fig. 14-26, p.537

33. Fig. 14-27, p.538

34. Fig. 14-5, p.512